Some examples of conventional techniques for preventing nuisance calls are described in JP2012-70246A. JP2012-70246A discloses a technique for extracting, from incoming history information of a telephone, a telephone number of a caller that corresponds to the condition in which a number of calls made per unit of time is greater than or equal to N times, and a call time is smaller than or equal to M seconds, and to reject an incoming call from this caller.